1. Field of the Invention
This invention relates generally to Videotex systems and more particularly is directed to a user terminal for use in such Videotex systems.
2. Description of the Prior Art
A Videotex system is a system for transmitting information, in the form of pages of text and color graphics, over the telephone lines from an information center providing electronic information services to a user terminal at which the information may be viewed page by page on a display screen. The system can provide users with information from many different sources, such as banks, newspapers, businesses and private information networks.
In Videotex systems, the information is organized into successive pages of information, each page corresponding to one complete image on the display screen. Each page is identified within the system by a number or other identifier which is displayed on the screen simultaneously with the information. The user terminal conventionally includes a display apparatus, such as a CRT having the display screen on which the successive images are displayed, and a keypad including a plurality of keys for controlling the user terminal and for entering data. In order to access information from the information center, the user inputs commands at the user terminal by operating the keypad and image data corresponding to requested pages is transmitted from the information center over the telephone line to the user terminal. Some commands request specific subject matter or pages, and frequently instructions for entering other commands will be included in the received information itself.
When the telephone link between the user terminal and the information center is disconnected, either intentionally or accidentally, the user must redial to reestablish the telephone link. However, redialing initializes the Videotex system, so that the user is returned to the initial page of information rather than to the page which was being viewed at the time of disconnection. If the user could remember the number of the page last viewed, that page number could be entered directly to resume use without significant interruption. There are, however, hundreds of thousands of pages available, making it very unlikely that the user will remember the correct number. As a result the user must step through the pages of information, duplicating the previous search, in order to rediscover the desired page. This process is time consuming and vexatious, and represents a significant disadvantage in the use of Videotex systems.